For example, an image forming apparatus using electrophotographic system uniformly charges a photosensitive body (a scan object) surface, scans the photosensitive body surface with light beam, and forms an electrostatic latent image at the photosensitive body surface. Then, the image forming apparatus develops the electrostatic latent image on the photosensitive body surface with toner to form a toner image on the photosensitive body surface, and transfers the toner image from the photosensitive body to a recording paper sheet.
A light scanning device scans the photosensitive body surface with the light beam. This light scanning device includes a light-emitting element such as a semiconductor laser, a plurality of mirrors such as polygonal mirrors, and a plurality of lenses such as fθ lenses. The light-emitting element emits a light beam. The polygonal mirrors reflect the light beam. The plurality of lenses deflect the light beam. The light beam from the semiconductor laser is guided to the photosensitive body surface by an optical member such as the respective mirrors and the respective lenses. The photosensitive body surface is scanned with the light beam, thus an electrostatic latent image is formed on the photosensitive body surface.
With the light scanning device, a position and a direction of a light emission surface of the light-emitting element need to be adjusted at high accuracy so as to form a condensation spot of the light beams on the photosensitive body surface. Additionally, a position of a main-scanning line on the photosensitive body surface with the light beam needs to be set.
For example, the light-emitting element is mounted on a substrate. After the substrate is mounted on an apparatus main body, a mounting position on the substrate to the apparatus main body is adjusted, thus the position and the direction of the light emission surface of the light-emitting element are adjusted. However, to make the mounting position on the substrate adjustable, increasing a size of a hole at the substrate through which a securing screw is passed, or providing a margin for the mounting space for the substrate is required.
Regarding color images, light-emitting elements corresponding to respective magenta, cyan, yellow, and black are required. However, if the respective light-emitting elements are mounted on a single common substrate, even if the mounting position on the common substrate is adjusted, the position and the direction of the light emission surfaces of the respective light-emitting elements cannot be individually adjusted. Accordingly, in Patent Literature 1, the respective light-emitting elements are mounted on different substrates, and the mounting positions for these substrates are adjusted. However, in this case, the number of components of the respective substrates or a similar component is increased. Additionally, margins need to be provided to the mounting spaces on the substrates depending on the respective substrates. Thus, the apparatus main body will be a large size.
It is also possible to adjust the position and the direction of the light emission surfaces of the light-emitting elements, secure the light-emitting elements to the apparatus main body, and then mount the light-emitting elements on the substrates. For example, in Patent Literature 2, optical axes of respective light-emitting elements corresponding to magenta, cyan, yellow, and black are adjusted. The respective light-emitting elements are secured to a housing of an apparatus. Afterward, terminals of the respective light-emitting elements are inserted into respective sockets secured to a single substrate, thus the substrate is secured to a specified position. However, positions of the terminals of the respective light-emitting elements secured to a housing and positions of the respective sockets, which are secured to the substrate, may be shifted. If this happens, it is difficult to insert the terminals of the respective light-emitting elements into the respective sockets, or a load is applied on the terminals of the respective light-emitting elements, resulting in shifting of positions of the optical axes of the respective light-emitting elements.
That is, in the case where a light-emitting element is mounted on the substrate and then the mounting position on the substrate is adjusted like disclosed in Patent Literature 1, a margin for the mounting space on the substrate needs to be provided, causing a problem of a large-size apparatus main body. Alternatively, like disclosed in Patent Literature 2, in the case where the light-emitting elements are secured, and then the terminals of the light-emitting elements are inserted into the sockets on the substrate to secure the substrate to a specified position, if the positions of the terminals of the light-emitting elements and the position s of the sockets on the substrate are shifted, it is difficult to insert the terminals of the light-emitting elements into the sockets, and a load is applied on the terminals of the light-emitting elements, casing a problem of shifting of positions of optical axes of the light-emitting elements.
On the other hand, to a substrate on which the light-emitting elements are mounted (referred to as a drive substrate), a driving circuit for light-emitting elements is formed. A control substrate at which a control circuit for controlling the driving circuit is formed is coupled to this drive substrate. For example, in Patent Literature 3, a drive substrate and a control substrate are coupled via a flexible harness. However, with a configuration where a laser diode that emits a plurality of light-emitting elements and multibeam is employed, the number of wirings coupling the respective substrates is increased. Accordingly, an influence of noise to the harness is increased. In view of this, it is preferred that connectors of the respective substrates are directly coupled to one another (Board to Board).
However, as disclosed in Patent Literature 1, in the case where the light-emitting element is mounted on the drive substrate, and then the mounting position on the drive substrate is adjusted, the position of the drive substrate changes. Accordingly, the position of the control substrate first needs to be aligned at the position of the drive substrate, and then a connector of the control substrate needs to be coupled to the connector of the drive substrate. Accordingly, a sufficient margin needs to be provided at the mounting space on the control substrate, resulting in a large-size apparatus main body. In the case where the mounting positions on the respective drive substrates on which the respective light-emitting elements corresponding to magenta, cyan, yellow, and black are mounted are individually adjusted, since positional relationships of the connectors of the respective drive substrates change, coupling connectors of a single control substrate to the connectors of the respective drive substrates is substantially impossible.
As disclosed in Patent Literature 2, in the case where the light-emitting elements are secured and the terminals of the light-emitting elements are inserted into the sockets of the drive substrate to secure the drive substrate to the specified position, coupling the connector of the drive substrate to the connector of the control substrate is easy. However, it is difficult to insert the terminal of the light-emitting element into the socket, leaving a problem that a load is applied on the terminals of the light-emitting elements or a similar problem.